A 'production guidance' downgrade occurs when the anticipated...

A 'production guidance' downgrade occurs when the anticipated production costs increase. That happens when either the target gold quantity needs to be reduced (for various reasons), or the target AISC increases (for various reasons), or both of those things happen together (reduced gold quantity with increased AISC).

Looking at page 2 (or page 27) of the Jan'18 presentation, the next 3.5 years (2018, 2019, 2020 & the first half of 2021) had an AISC guidance of $1100-$1200 / oz gold. Page 7 also shows a gold quantity guidance of 40k-45k oz with an AISC of $1100-$1200 for the period of Jan'18 - Jun'18. IMO the 'production guidance' was downgraded for CY2018 (calender year) as soon as BLK announced an increased AISC of $1250-$1450 / oz on 18th July. The announcement had a pronounced adverse effect on the SP.